Several RNA viruses are now known to be capable of binding a specific amino acid at their 3'-terminus, in a transfer RNA-like manner. The function of this property is not known. It has been found that elongation factor EF 1 will bind to aminoacylated, but not to uncharged, viral RNA molecules. EF 1 has a similar function to the bacterial factor EF Tu, which is identical to a subunit of Q beta replicase. The possibility exists that the binding of one replicase enzyme subunit to the viral RNA could result in preferential attachment of the other replicase subunits. Under appropriate conditions, Q beta replicase will efficiently transcribe RNA from brome mosaic virus (BMV). BMV is a virus of divided genome, whose RNA components can be enzymatically charged with tyrosine. We propose to purify BMV RNA components, Q beta replicase, and EF 1 from wheat germ. We will then compare the efficiency of transcription of the viral RNA components in their native state, after aminoacylation, and after modification to prevent aminoacylation. If the charged viral RNA represents a significantly better transcriptional template, this will be strong evidence that the aminoacylation property is advantageous to the virus through enhancing chances of viral RNA replication following entry to the host cell.